I guess maybe it was your seat. When I saw it at the Palladium I didnt know what all the fuss was about. The arm was clearly visible all the time from where I was.
Think of one of those trucks with the arm and bucked that they use to fix utility poles, it starts out horrizontal then the arm moves up and extends, but instead of a bucket on the end, they have the car. The car on the end can pivot and rotate also.
http://www.flickr.com/photos/27199361@N08/ Phantom at the Royal Empire Theatre